The "default" setting of 4e is an amalgam of many things with no precisely given names or constraints for things like names of days/months or how long any of these things truly are. You should look to a specific setting released for 4e for its own individual answers, but the 'base' or 'default' of 4e is for you to basically make up whatever you like, or pull in this information from back catalog materials.

I ran a 4e Ravenloft game using 2e materials and ported everything over just fine, stuff like this seems to have little effect on the system itself, all a matter of preference really.